Fishing Moratorium Research Articles

A coastal lagoon-spawning Winter Flounder subpopulation during ecosystem and fisheries shifts

Abstract Objective This research collates numerous data sets, including long-term fisheries monitoring surveys, predators, water quality, and fishing pressure, to explore possible biotic and abiotic correlates that may be hindering the recovery of a Winter Flounder Pseudopleuronectes americanus subpopulation. Methods Age-0 (i.e., young-of-year) Winter Flounder and spawning contingents within a single coastal lagoon, Point Judith Pond (Rhode Island), were evaluated across two decades (1999–2020) to determine how potential ecological drivers and harvest have contributed to the subpopulation's state. Available data sets describing predators of both age-0 and adult Winter Flounder, fecal coliform measurements, water temperature, and commercial and recreational harvest were run in a correlative analysis with age-0 and adult Winter Flounder. Result Despite decreases in fishing mortality within the pond, there has been no recovery within the Point Judith Pond subpopulation—a shared response across the stock unit. Although it is possible that an increase in predators of eggs, age-0 Winter Flounder, and spawning adults may be hindering the recovery of this subpopulation, other characteristics, such as water quality, habitat degradation, and prey availability, may also be important contributing factors. The survival rates of age-0 Winter Flounder through their first summer appear to have been relatively unchanged over the course of the research, but there has been a contraction in both the spawning period and the maximum size of adult female Winter Flounder in the study area. Conclusion By the time a fishing moratorium was implemented in Point Judith Pond, Winter Flounder abundance was already below time series historic minimums. With fishing pressure seemingly no longer regulating population size, other management strategies must be developed to address natural mortality and habitat degradation. Abstract Impact statement Despite two decades of monitoring multiple life stages of a Winter Flounder subpopulation within a single coastal lagoon under limited fishing pressure, identification of the biotic and abiotic bottlenecks to population recovery remains elusive.

From dynamics to sustainability: Modeling the shrimp (Penaeus chinensis) fishery in Shandong, China

Since 1984, the stocking of shrimp juveniles has been implemented in the Bohai Sea, China as a strategy to manage the depleted marine fishery. Subsequently, major harvest restriction policies including “Dual Control” (1987), “Summer Fishing Moratorium” (1995), and “Fishermen Transfer and Fishing Fleet Scraping” (2003) were gradually implemented to reduce fishing intensity. However, the relative effectiveness of these three policy changes and management improvements, such as varying stocking quantity, adjusting the duration of the summer fishing ban, and reducing fishing intensity rate have rarely been assessed before their implementation. To address this gap, we developed a System Dynamic model that incorporated multiple scenarios related to these strategies in the shrimp fishery. Using Penaeus chinensis shrimp in the coastal province of Shandong, China, as a test case, we simulated the harvest metrics and stock size for each scenario. Our model predictions revealed that among the three strategies, extending the duration of the summer fishing ban is the most likely to improve the harvest metrics, while reducing fishing intensity significantly increases shrimp abundance. Based on the research findings, we recommend an optimal combination of the three strategies: releasing approximately 700 million individual juveniles per year, decreasing the fishing intensity rate to 0.65, and increasing the duration of the summer fishing ban to 123 days, from 1 May to 31 August. The research outcomes contribute to evidence-based decision-making and sustainable management practices in the Bohai Sea shrimp fishery and beyond.

Recognizing topological attributes and spatiotemporal patterns in spotted seals (Phoca largha) trophic networks based on eDNA metabarcoding

Spotted seals, a protected species, face multifaceted threats to their habitat, which in turn impact the closely associated trophic networks. These threats will lead to irreversible structural variations within the ecosystem. Therefore, investigating the topological variability of trophic networks in spotted seals is important. Applying environmental DNA methods, field sample collection was conducted in 2021 during both the sea fishing moratorium period and the fishing period to decode fish diversity. Assessing the current status of fish resources by using the multivariate statistics approach. Applying dietary information establishes the spotted seals’ trophic network. Selecting 12 network indexes to analyze the spatiotemporal patterns of network topological attributes. As a result, about 51 families, and 76 genera species were identified. During the sea fishing moratorium and the fishing period, there are 12 and 18 different food resources available for spotted seals, respectively. The diversity index revealed that the FP had greater species richness and diversity than the SP. Comparatively, the Fishing period exhibited higher species richness and biodiversity, likely influenced by habitat heterogeneity and anthropogenic activities. Additionally, the topological features of networks reflected the high clustering coefficients (CC=0.35) and the proportion of omnivorous species (O≈60%), indicating that the network structure in this region tends to form higher trophic-level clustering patterns, which facilitate the formation of weaker interactions between clusters, enhancing the robustness of the network. The higher connectivity complexity index during the fishing period (SC=12.3) supported that the spotted seal’s trophic network was relatively more stable in this period. Thus, during the fishing period, it is crucial to pay more attention to the intensity of human fishing on mid-to-high trophic-level omnivorous fish resources to ensure the sustainability of these potential food resources for spotted seals. This comprehensive study achieved three key objectives: (a) utilizing eDNA to characterize fish diversity during distinct periods, (b) establishing trophic networks of spotted seals, and (c) discerning topological attributes and spatiotemporal patterns within the ecological network. Overall, this study can provide technical and data support for integrated ecological network management and propose suggestions for protecting and recovering spotted seals.

Assessment of ecological damage from illegal fishing and judicial practice for damage compensation

In the context of China's comprehensive trial of an ecological damage compensation system, the lack of a widely accepted assessment model for assessing ecological damage caused by illegal fishing will inevitably affect the fairness of judicial rulings and the success of ecological restoration. In this study, we examined a typical illegal fishing case with a significant impact in China to illustrate the multi-dimensional damage caused by bottom trawls to the offshore ecosystem during a fishing moratorium as the first step in establishing a unified enforcement standard. Based on existing research, damage is divided into two types: quantifiable and unquantifiable. The former mainly refers to the ecological damage corresponding to illegal catches, while the latter includes habitat damage, mortality after escape, disturbance of spawning behaviour, and potential egg losses related to illegal catches. Quantifiable damage is the main basis for judging ecological environmental damage compensation cases, but it has not been fully utilized due to the lack of guiding documents. For unquantifiable damages, the “judicial discretion” of judges may be an effective measure to deal with this challenge. In addition, a preliminary amount correlation among two damage types was established based on a weight-based expert scoring method. This study provides a reference for China to establish a compensation mechanism for the ecological damage caused by illegal fishing in the future and can be applied to other regions plagued by illegal fishing around the world.

Is a Fishing Moratorium Needed in Lake Honghu, Southern China? A Stomach Content Analysis of the Anchovy (Coilia brachygnathus)

Since 2017, a fishing moratorium has been enforced in Lake Honghu as part of Chang–Jiang’s biodiversity conservation strategy. However, given that the lake is a semi-closed aquatic ecosystem and no longer serves as a habitat for certain fishes of the mid–lower Chang–Jiang basin, the efficacy of this moratorium remains uncertain. To address the question from a trophic ecology perspective, a stomach content analysis was performed on captured anchovies of C. brachygnathus, a current predominant species in Lake Honghu, from November 2020 to October 2021. The results showed that copepods, shrimps, and macrophytes were the main components of this anchovy’s diet, and there were size-related shifts in diets. The dominance of C. brachygnathus, a pelagic–littoral omnivore in this lake, implies a lacustrine environment shift triggered by continued human disturbances. The utilization of macrophytes as the main food items by large-sized anchovies of Lake Honghu has partially contributed to the rapid degradation of submerged vegetation. This highlights the need to remove large-sized individuals of C. brachygnathus and Carassius auratus, another benthic-omnivorous dominant fish, in order to effectively restore the aquatic vegetation and ecosystem of Lake Honghu. The current implementation of fishing moratoriums in subtropical shallow floodplain lakes such as Lake Honghu should be reviewed critically.

Ambient black carbon variations and emission characteristics of typical Chinese vessels in the Yangtze River Delta, China.

Black carbon (BC) has a significant impact on air quality, climate change, and human health. Studies on BC from vessel exhaust have been focused on in recent years. To realize the contribution of BC from vessels to ambient air quality, 28 months of BC variation were observed from February 2019 to May 2022, including 3 fishing moratoriums and 2 normal periods. The results showed that the average daily concentration of BC in the fishing moratorium was significantly lower than that in the normal period. The difference proportion of the BC concentration between 370 and 880 nm was calculated over the whole period. As a result, the mean difference value in the fishing moratorium from February to May was 0.06 ± 0.07, and the normal period was -0.02 ± 0.05. The aethalometer model indicated that BC was greatly affected by fossil fuel combustion in the normal period. The effect of vessel emissions on regional BC concentrations was considerable. In addition, 16 PAHs and 21 elements in PM emitted from 24 vessels of different types were sampled and analyzed in Dianshan Lake and the Taipu River. EC accounted for the highest proportion (23.64%) in the sample of small trawlers compared to the emissions from cargo ships with large tonnages. The component profiles of vessel exhaust showed that Zn, As, phenanthrene (Phe), anthracene (Ant), fluoranthene (Fla), and pyrene (Pyr) were the dominant species, although some of these species were mainly recognized as characteristic factors of coal combustion. To improve the accuracy of identifying the vessel source, the diagnostic ratios of Ant/(Ant + Phe), BaA/(BaA + Chr), Phe/Ant, and BaA/Chr were provided, and they exhibited the obvious characteristics of fuel combustion.

Cooperation: A Systematic Review of how to Enable Agent to Circumvent the Prisoner’s Dilemma

It is widely accepted that rational individuals are unable to create cooperation in a prisoner’s dilemma. However, in everyday life, cooperation, for example, during a fishing moratorium, can be observed frequently. Additionally, the appearance of cooperation in the prisoner’s dilemma can be seen in numerous simulation studies. This paper reviews 31 simulation studies published between January 2017 and January 2023 in which agents can be observed in the results to improve cooperation in a prisoner’s dilemma. The proposed methodologies were sorted into seven categories, including Bounded Rationality, Memory, Adaptive Strategy, Mood Model, Intrinsic Reward, Network Dynamics, and Altruistic Attribute. Based on their impacts, the effectiveness of these seven approaches was classified into three categories: generating cooperation, maintaining cooperation, and spreading cooperation. This review is expected to be helpful for scholars conducting future research on multi-agent cooperation and irrational agent modeling.

Incidental fishing of Epinephelus itajara (Lichtenstein, 1822): the vulnerability of a critically endangered species of the Brazilian coast

Epinephelus itajara, popularly known as grouper, has a wide distribution and is considered the largest fish in the Atlantic Ocean. Behavioral characteristics allied to overfishing and degradation of marine habitats caused declines in E. itajara populations throughout the entire geographic distribution area. The goliath grouper is currently ranked on the IUCN RedList as Vulnerable in Global Status and Critically Endangered in the Gulf of Mexico. In Brazil, even with a fishing moratorium that has protected it since 2002, the species is categorized as critically endangered in the Red Book of the Instituto Chico Mendes de Conservação da Biodiversidade. Taking into account these factors and the information gap on the goliath grouper, this study addresses an account of an occasional “post mortem” encounter with a specimen on the edge of Pajuçara beach, Maceió - Alagoas. It was an adult individual, whose size was estimated at 1.6 m and 70 kg of body mass. This study also presents discussions about the conservation status of the species and the efficiency in the management of marine protected areas, revealing that even with many marine protection areas, incidental captures and port records are still recurrent on the Brazilian coast. This record highlights the need to reinforce inspections, in addition to suggesting that the management of these areas be more efficient, ensuring the reestablishment of grouper populations in the region.

Modeling the Effects of Seasonal Fishing Moratorium on the Ecosystem of the Minjiang Estuary in Southeastern China

China’s marine fisheries have made a huge contribution to the world’s food supply at the expense of wild resources collapse by overfishing. Accordingly, the government has introduced a series of measures represented by seasonal fishing moratorium to achieve sustainable fisheries. To evaluate the impact of the seasonal fishing moratorium on the ecosystem of the Minjiang Estuary in southeastern China, three ecosystem models, one in 2006, one in 2016 after 10 years seasonal fishing moratorium, and one in 2016 simulated under the scenario without a fishing moratorium, were constructed by Ecopath with Ecosim. Based on the 2016 model, the status of the Minjiang Estuary ecosystem after 50 years was simulated under four scenarios of different combinations of fishing pressure and durations of the fishing moratorium. The results showed that in the 2016 model, parameters as total ecosystem flow, mean fishing trophic level, and Finn’s index were 9,235.407 t km−2 year−1, 2.94, and 0.920, respectively, all significantly higher than those extracted from the 2016 simulated model, suggesting the effectiveness of the seasonal fishing moratorium. Under scenario analysis, extending the fishing moratorium by 3 months and reducing fishing pressure by 50% showed synergistic effects to achieve a better result than the current fishing moratorium strategy.

The Satisfaction of the Fishermen in the South China Sea With the Summer Fishing Moratorium System and Its Influencing Factors

This study investigated the satisfaction of fishermen with the summer fishing moratorium system in the three provinces of the South China Sea through a questionnaire survey and explored the degree of its influencing factors. A multistage random sampling method was used to issue questionnaires to fishermen involved in the summer fishing moratorium. A total of 258 valid questionnaires were collected, and the factors were analyzed them using the factor analysis method by SPSS 23.0 software. The results showed that the variance contribution rate of the first five factors reached 61.859%, and the 11 factors that have potential commonality in influencing fishermen’s satisfaction with the fishing moratorium can be summarized and classified into five more significant factors, such as “economic income during fishing moratorium (16.396),” “illegal fishing boat (12.095),” “fishing moratorium time (12.012),” “law enforcement credibility (11.853),” and “summer fishing moratorium effect (9.503).” According to the factor score calculation, the fishermen’s satisfaction with the fishing moratorium was F = 3.53, and the overall satisfaction was relatively high. This study reveals the satisfaction degree of the fishermen in the South China Sea with the summer fishing moratorium system and its influencing factors, which can provide a basis for improving the summer fishing moratorium system and ensuring the lives of fishermen.

Temporal Dynamics of Fishing Affect the Biodiversity of Macrobenthic Epifaunal Communities in the Coastal Waters of Ningbo, East China Sea

Spatio-temporal patterns of macrobenthic epifaunal communities with fishing disturbances indicate that the fishing process directly leads to a decrease in diversity and substratum sediment homogenization. However, it has not yet been explored exclusively at the community reconstruction dynamic level with fishing changes over time. This study monitored the macrobenthic epifaunal communities during the implementation of a fishing moratorium policy in order to elucidate the fishing-driven variations in the macrobenthic epifaunal communities. Bottom trawl surveys were conducted before (BEF), during (DUR), and after (AFT) a summer fishing moratorium. During each survey, macrobenthic species and surface sediment samples were collected from two transects located at two different depths. The results showed that the communities in the DUR phase were undisturbed, while the communities were disturbed in both the BEF and AFT phases. Compared with the BEF and AFT phases, there was an abundance of peak spawning species as well as the impact on macrobenthic communities in relation to the lightened fishing disturbance, significant increases in species richness, abundance, and biomass were observed in the DUR phase. Prohibition of fishing during summer facilitates the resilience of macrobenthic communities by maximizing spawning and reducing bottom disturbance to larval, thereby enhancing overall fishery resources.

Capelin (Mallotus villosus) availability influences the inshore summer diet of Atlantic cod (Gadus morhua) in coastal Newfoundland

In the early 1990s, the Atlantic cod (Gadusmorhua) population on the Newfoundland and Labrador shelf declined dramatically, leading to a fishing moratorium in 1992. The Northern cod population has not fully recovered, possibly due to the simultaneous population collapse of an important prey type, capelin (Mallotus villosus), which migrates from the continental shelf into coastal Newfoundland to spawn every summer. Our objective was to test whether capelin availability influenced short-term dietary shifts of cod while inshore on the northeast Newfoundland coast. We quantify the dietary composition and relative abundance and biomass of prey types in cod stomachs sampled weekly or bi-weekly throughout July-August 2017 and 2018. Survey-based acoustic estimates of capelin biomass and the timing of spawning in the study area revealed that peak capelin biomass was five times higher (0.239 g/m²) and two weeks earlier (July 28) during 2018 relative to 2017 (0.048 g/m², August 9). Cod stomachs were ~ 10 times more likely to contain capelin during 2018 relative to 2017. As capelin availability increased throughout each summer, cod shifted from a high diversity diet of lower-quality invertebrate prey (e.g., shrimp, crab) to a low diversity, capelin-dominated diet, whereby capelin presence, abundance and biomass increased. These findings indicate that capelin remains a primary prey type of cod in inshore waters during their summer growing season, but dietary proportions of capelin vary with their availability. As low dietary proportions of capelin are associated with reduced body condition and reproductive potential in cod, findings support the need for an integrated capelin-cod management approach.

Implications of Allee effects for fisheries management in a changing climate: evidence from Atlantic cod.

There are concerns that increasing anthropogenic stressors can cause catastrophic transitions in ecosystems. Such shifts have large social, economic, and ecological consequences and therefore have important management implications. A potential mechanism behind these regime shifts is the Allee effect, which describes the decline in realized per capita growth rate at small population density. With an age-structured population model for Atlantic cod, Gadus morhua, we illustrate how interactions between human-induced stressors, such as fishing and climate change, can worsen the impact of an Allee effect on populations by promoting hysteresis. Therefore, the risk of population collapse and recovery failure is exacerbated and the success of preventing and reverting collapse depends on the climate regime. We find that, in presence of the Allee effect, a fishing moratorium is only sufficient for recovery when sea surface temperature rise remains within 2°C and fishing is restricted within 10yrs. If sea surface temperature rises beyond 2°C, even immediate banning of fishing is not sufficient to guarantee recovery. If fishing is not fully banned and a residual fishing pressure remains, the probability of recovery is further decreased, also in the absence of an Allee effect. The results underscore the decisive role of Allee effects for the management of depleted populations in an increasingly human-dominated world. Once the population collapses and its growth rate is suppressed, rebuilding measures will be squandered and collapse will very likely be irreversible. We therefore emphasize the need for proactive management involving precautionary, adaptive measures and reference points. Our studies shows that climate change has the potential to strengthen Allee effects, which could increasingly challenge fisheries management.

Golden cod persist through climate change

This “golden cod” (left) from Gilbert Bay, off the coast of Labrador, Canada, is easily recognized by commercial harvesters because of its distinctive “golden” coloration; this fish is technically an Atlantic cod (Gadus morhua), though it is much darker than cod from the adjoining northern population (right). Atlantic cod is a population-rich species, incorporating tremendous intraspecific biodiversity, and is prized by North Atlantic fisheries. The northern cod stock, which collapsed and was placed under a fishing moratorium in 1992, has not recovered owing in part to colder-than-normal ocean temperatures in the Labrador Sea. Remarkably, while northern cod experienced high rates of natural mortality during the 1990s, the Gilbert Bay cod population grew. This golden cod spent its entire life (~17 years) in Gilbert Bay, living 6 months of the year just meters beneath sea ice in sub-zero temperatures. It therefore experienced much colder conditions, and for longer time periods, than other Atlantic cod. During summer, however, golden cod take advantage of the short growth season in the shallow waters that warm quickly within the protection of the bay.

Explorative GPS-Tracking of Foraging Movements by Audouin's Gulls Reveals No Association with Fishing Vessels in Croatia

The Audouin's Gull Larus audouinii is endemic to the Mediterranean, with the majority of the global population concentrated in Spain. It mainly feeds on small pelagic fish during the night; however, there is more variation in the foraging behaviour of the Ebro Delta population, with birds also feeding during the day and inland. This plasticity was identified as one of the main factors involved in the increase in population size since 1980. However, foraging movements have only been poorly studied in other populations. We studied the movements of Audouin's Gulls breeding in the small, endangered Croatian population, foraging at the Adriatic Sea, and compared their behaviour with that of conspecifics in the increasing Spanish population in Ebro Delta. Five incubating adults were equipped with a GPS-GSM solar-powered tracking device. We analysed characteristics of short and long foraging trips, differences in movement patterns between sexes and between night and daytime, and the association of gulls with fishing vessels. Daily average trip lengths were similar for all birds, while individual patterns were very diverse. Birds undertook both short (up to 45 km) and long-distance trips (up to 256 km), with length of trips, trip duration and the maximum distance being greater for females. The comparison of gull GPS-fixes with tracking data (VMS) of purse seine fishing vessels showed that birds from the Croatian population, in contrast to the Spanish birds, did not associate with fishing vessels, nor did their foraging behaviour change as an effect of a fishing moratorium. Our results showed that long-distance movements were longer and more frequent than those recorded in other populations, which suggests that depending on non-anthropogenic resources may result in a high cost of chick-rearing.

Fecundity of haddock (Melanogrammus aeglefinus) off southern Newfoundland

Reproductive life history parameters, such as size-specific fecundity, can contribute to our understanding of fish population dynamics. However, most of these parameters are difficult or time-consuming to obtain. Therefore, previously calculated parameters are often used in combination with more easily collected metrics of size. Significant temporal variation in fecundity is known to occur in many fish species, meaning that previous estimates may be unreliable when examining contemporary fish stocks. For southern Newfoundland haddock, the only published fecundity data were collected more than 50 years ago when this species supported a major fishery in the area. Here we present fecundity data collected during the 1960s immediately following stock collapse, as well as data from 2013 to 2014 (after 20 years of a fishing moratorium) and examine potential differences in egg production among the time periods. Contemporary estimates of haddock fecundity were more similar to estimates of fecundity immediately following stock collapse than estimates during the period of maximum exploitation. Additionally, comparison of haddock fecundity throughout the northwest Atlantic Ocean revealed contemporary estimates from southern Newfoundland to generally be higher than those from the Scotian Shelf for haddock at all lengths as well as greater than those from George’s Bank until about 60 cm in total length. The ability of various fish characteristics (length, weight, age, and condition) to serve as metrics of haddock fecundity were investigated and found that while length was the best predictor of fecundity, explanatory power was relatively low (maximum R2 = 0.37), and there was little to no effect of fish condition on fecundity. Inter-annual variability in fecundity estimates, coupled with the lack of a suitable proxy for fecundity for Newfoundland haddock suggests that ongoing monitoring is required to accurately estimate reproductive potential.

Exploitation status of Squaliobarbus curriculus in the Xijiang River based on the analysis of the yield per recruit and spawning biomass per recruit models

PDF HTML阅读 XML下载 导出引用 引用提醒 基于单位补充量模型的西江赤眼鳟种群资源利用现状评价 DOI: 作者: 作者单位: 1. 中国水产科学研究院珠江水产研究所, 广东 广州 510380;2. 上海海洋大学海洋科学学院, 上海 201306;3. 农业农村部珠江中下游渔业资源环境科学观测实验站, 广东 广州 510380 作者简介: 李策(1993-),男,硕士研究生,从事渔业资源研究.E-mail:lice930811@aliyun.com 通讯作者: 中图分类号: S931 基金项目: 广东省自然科学基金项目（2016A030313147）；中国水产科学研究院中央级公益性科研院所基本科研业务费专项资金（2017HY-ZD0103）. Exploitation status of Squaliobarbus curriculus in the Xijiang River based on the analysis of the yield per recruit and spawning biomass per recruit models Author: Affiliation: 1. Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510380, China;2. College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China;3. Scientific Observing and Experimental Station of Fishery Resources and Environment in the Middle and Lower Reaches of Pearl River, Ministry of Agriculture and Rural Affairs, Guangzhou 510380, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:赤眼鳟（）是珠江中下游最重要的经济鱼类之一，本研究利用2009—2014年西江肇庆江段渔业捕捞调查监测数据，分析了其生长和死亡参数历史变化，利用单位补充量渔获量（yield per recruitment，YPR）模型、单位补充量产卵群体生物量（spawning biomass per recruitment，SBR）和生物学参考点评估了赤眼鳟资源利用状况。结果表明，赤眼鳟体长（R2=0.9595，+0.613）]。目前西江的捕捞强度（=0.86）远超种群可持续开发水平，赤眼鳟种群处于生长型捕捞过度状态。根据实际情况，建议将西江赤眼鳟开捕年龄提高至3龄（或开捕体长增大至238 mm），则预计单位补充量渔获量可增加175%，在珠江禁渔期制度的协同保护下，种群实际保护效果可能更好。 Abstract:The Pearl River, the largest river in southern China, historically harbors abundant fishery resources. However, the fishery resources have severely declined in recent decades owning to dam cascade development, overfishing, water pollution, and so on. Therefore, it is necessary to evaluate fishery resource utilization and exploitation, which provides scientific guidance for fishery resource conservation in the Pearl River. Generally, the per recruitment model has been widely applied to the dynamics of single fish populations. The per recruitment models mainly consist of the yield per recruitment model (YPR) and the spawning biomass per recruitment models (SBR). The YPR model prevents overgrowth overfishing and is usually used to determine the fishery management parameters (e.g. mesh size and catch rate). This model could provide management guidance for the development and utilization of fish stocks. The spawning biomass per recruitment model prevents supplemental overfishing. This model is utilized to assess whether parental biological residues and spawning stock are sufficient to maintain the stock of larvae supplementation, and then it estimates the status of resource utilization. The barbel chub () is an important economic fish inhabiting the middle and lower reaches of the Pearl River. An assessment of the current status of utilization is important for reasonable resource exploitation and maintenance. The data of the present study were collected in the Zhaoqing section of the Xijiang River (an important stem of the Pearl River) between 2009 and 2014. We analyzed the growth and mortality characteristic parameters and evaluated the resource exploitation status by the YPR model, SBR model, and biological reference points. The relationship between standard length and weight was expressed as:=0.9595, =2346). The von Bertalanffy growth equation was selected as the optimal growth model and was expressed as ]. The present fishing intensity (=0.86) have far exceeded the level of sustainable population development. The stock of was overfished in its vegetative form. We suggest to increase the catch age to 3 years old (or to a standard length of 238 mm) for the stock conservation of in the Xijiang River; the yield per recruitment could thus be increased by 175%. The protective efficacy could increase with a fishing moratorium in the Pearl River, and relevant fishery management measurements should be improved at the same time. 参考文献 相似文献 引证文献

Fifty-five-year longevity for the largest member of the family Sparidae: the endemic red steenbras Petrus rupestris from South Africa

A previous study that explored the age and growth of red steenbras Petrus rupestris (Valenciennes, 1830), a large sparid (family Sparidae, seabreams or porgies) endemic to South Africa and reported to approach 2 m in length, provided estimates as a moderately slow-growing species with a maximum age near 30 years. The stock is considered collapsed and a fishing moratorium was imposed in 2012, resulting in this species being assessed as Endangered by the IUCN. One consideration in addressing population status is validation of life-history traits. In this study, estimates of age for red steenbras from thin-sectioned otoliths were reassessed visually in terms of both the original ages and revised estimates using a different age-reading pattern. The revised ages exceeded the original ages by up to 30 years, with a maximum estimated age of 55 years from a well-defined otolith section that provided a basis for the revised age-reading procedure. Bomb radiocarbon (14C) dating revealed there was an offset in the timing of the 14C rise on the Agulhas Bank that, when coupled with considerations for regional oceanography, provided support for the revised age-reading pattern and an estimated longevity that exceeds 50 years. These findings were further supported by the fortuitous recapture of a tagged red steenbras that was at liberty for 22 years.

Impact of a fishing moratorium on a tuna pole-and-line fishery in eastern Indonesia

Indonesia's fisheries sector is contributing significantly to the strategy of national sustainable development, not least because regulations have been developed by the government to manage and maintain its tuna resources. One of these regulations was a moratorium established on fishing licences for foreign and ex-foreign fishing vessels in the Indonesian fisheries management area from 3rd November 2014–31 st October 2015, the rationale being to reduce illegal, unreported and unregulated fishing activities. Since the impact of this moratorium on small-scale coastal tuna fisheries has not yet been investigated, this research aimed to explore any short-term effects on pole-and-line tuna production by analysis of data on tuna landings and fishers’ perceptions in selected sites in eastern Indonesia. The landings of the pole-and-line tuna fishery decreased during the moratorium in Larantuka but no impact was found in Pulau Bacan or Sorong. However, the vast majority of fishers perceived that the moratorium had benefited their catch rates. The verdict on the effect of the moratorium on foreign and ex-foreign fishing vessels on the pole-and-line fishery in Indonesia is therefore moot, although it is conceivable that the main effect was to demonstrate engagement of the government with the international importance of this fishery.

Assessment on the Effects of Summer Fishing Moratorium in East China Sea

Assessment on the Effects of Summer Fishing Moratorium in East China Sea